This invention relates to a method of determining the average current drawn by an electric motor, and to related apparatus.
In many automotive applications, it is useful to be able to provide a measure of the battery current draw whilst a system is in operation. For large electrical components such as an electric power assisted steering (EPAS) system, it is common to transmit the battery current information to other components on the vehicle to enable load-levelling to be carried out to improve battery/alternator performance.
For cost-sensitive automotive applications, this ideally needs to be done without adding any cost to the system. However, for systems such as permanent magnet AC motor drives which use a single current sense series with the motor phases to measure the three phase currents, (for example, the circuit shown in EP 1 083 650 A2) it is not easy to directly measure the battery current, due to large fluctuations in drive current. An average current measurement is desirable.